1. Field of the Invention
The present invention relates to a process cartridge and an image forming apparatus, and more specifically to the process cartridge for forming images in a copying apparatus, a facsimile apparatus, a printer or the like by an electrostatic image transfer process, and to the image forming apparatus which uses the process cartridge.
2. Discussion of the Related Art
In an image forming apparatus of the type using an electrostatic image transfer system, a process cartridge is often used. The process cartridge collectively includes a photoconductive member and a process device e.g. a charging device, a developing device, a cleaning device and the like to form an image on the photoconductive drum. The process cartridge allows a user or a service person to replace the process cartridge currently installed in the image forming apparatus with a new one if maintenance or replacement of parts is needed in the installed cartridge. In the case that a service person can maintain the image forming apparatus, the maintenance time may be shorter because maintenance can be simply done. Also, a user can replace the process cartridge with a new one when a service person is unavailable.
In such an image forming apparatus, process devices should be accurately assembled within a process cartridge to form a higher quality image. Especially, unless a cleaning blade formed by a light rubber accurately contacts a photoconductive member, the cleaning blade can not adequately remove a residual toner so that an unusual image may be formed. For example, inaccurate contact may cause an undesirable change of pressure in a length direction, a change in cleaning angle, or the like of the cleaning blade. Conventional image forming apparatus include a cleaning blade and a photoconductive drum included in a removable process cartridge. However, many of these conventional designs mount the cleaning blade in the process cartridge without consideration of the accuracy of contact between the cleaning blade and photoconductive drum.
Japanese laid-open patent publication no. 5-134484 is directed to maintaining accurate contact between a photoconductive member and a cleaning device with a cleaning blade within a process cartridge. This reference shows a cleaning blade directly connected to a support plate, which in turn is connected to a strength frame formed of sheet material. The strength frame is coupled to a shaft by way of an L shaped member. The shaft is rotationally coupled to side plates of the process cartridge, so that the cleaning blade can rotate into and out of contact with the photoconductive member. A bias spring connected to a top wall of the process cartridge is coupled to the L shaped member in order to bias the cleaning blade toward the photoconductive drum. However the present inventors have recognized that such a complex support structure of interconnected parts can diminish the accuracy of contact between the cleaning blade and photoconductive drum.
Thus, there is a strong demand in which each cleaning member, e.g. a cleaning blade, a cleaning roller and the like, further accurately contacts on a photoconductive member to improve cleaning ability.